Hi, wondering if anyone has forund a source of clear 4.5mm tube? This would be great for a magazine to identify feeding problems but am at a loss as to where one would source it from. I dont know what uses it would have, I can only find it in glass at a medical supply place.

Go look for PET, clear PVC, acrylic or PC tubing. If you live in the Western world, you should be able to google up some vendors in your area.

The only problem with these types of thermoplastics is that they scratch rather easily. However, since your stated purpose is to check for leaks/jams/whatnot, a few scratches here and there shouldn't be much of a problem.

Personally, I regard using modelling stuff on spudguns as a waste of money, since you're essentially paying for some random brand name on otherwise "generic" products. Beside the ID/OD isnt' mentioned. Not worth the risk and effort IMO when you can probably get it much cheaper locally.